Intake systems for engines of motor vehicles are often designed with a fixed geometry, which is tuned to provide air to cylinders of the engine most effectively at a particular desirable engine running speed. The desirable engine running speed may be a speed at which the engine produces peak power or peak torque. Alternatively, the desirable engine running speed may be a speed at which the engine operates most efficiently when the vehicle is travelling long distances. Designing the geometry of the intake system such that it is tuned to a desirable engine speed may enhance the performance of the engine in this running condition.
Variable geometry inlet systems comprising variable length inlet ducts are available, which allow the tuning of the intake system to be varied during operation of the engine. However, packaging of intake systems is often tight, restricting the use of such systems.
In one example, the issues described above may be addressed by an intake system for an engine comprising: an intake duct configured to carry inlet air to cylinders of the engine; a chamber provided to one side of the intake duct and in fluid communication with the intake duct; a movable element provided within the chamber; and an actuator configured to vary the position of the movable element and thereby vary a volume of the chamber able to receive inlet air from the intake system; wherein the actuator is configured to vary the position of the movable element at a frequency, wherein the frequency varies according to the rotational speed of the engine.
The actuator may be configured to oscillate or reciprocate the movable element. The position of the movable element may be varied about a mean position.
The chamber may comprise a neck portion and a cavity portion, the neck portion having a smaller diameter than the cavity portion. A component of the mainstream flow velocity where the neck portion meets the intake duct may be perpendicular to a central axis of the neck portion, e.g. the central axis of the neck portion may be at an angle relative to the flow of inlet air within the intake duct where the neck portion meets the duct.
The intake system may further comprise an orifice configured to permit a flow of inlet air into and/or out of the chamber. The neck portion and the orifice may be separate or the orifice may form the neck portion.
The intake duct and/or the orifice may be configured such that a component of the mainstream flow velocity where the orifice meets the intake duct is perpendicular to a central axis of the orifice, e.g. an opening on the orifice. For example, the intake duct and/or the orifice may be configured such that the inlet air flowing within the intake duct may be directed at least partially across the orifice. The inlet air may also be directed at least partially into and/or out of the orifice, e.g. the opening of the orifice.
The engine may comprise one or more engine inlets. The engine inlets may be configured to selectively open to permit the inlet air to enter the cylinders.
The actuator may be configured to vary the position of the movable element according to the opening of the engine inlets, such as to vary the volume of the chamber according to the inlet which is opening, or is next to open.
The actuator may be configured to vary the frequency at which the position of the movable element varies according to the opening of the engine inlets, such as according to which inlet is open and/or which inlet is the next to open.
The actuator may be configured to vary a phase difference between the movement of the movable element and the rotation of the engine according to the opening of the engine inlets, such as according to which inlet is open and/or which inlet is the next to open.
The actuator may be configured to vary the position of the movable element and/or the frequency at which the position of the movable element is varied according to a distance between the chamber and the engine inlet that is being opened.
The chamber may be provided at a location substantially equidistant through the intake duct from a pair of the engine inlets. The intake duct may further comprise an inlet manifold configured to carry inlet gases to each of the cylinders. The chamber may be provide at one side of the inlet manifold. The chamber may be in fluid communication with the intake manifold. The chamber may be provided substantially centrally on the inlet manifold. The inlet manifold may comprise a first end and a second end, wherein the first end is closer to an air inlet of the intake system than the second end. The chamber may be in fluid communication with the inlet manifold at or near the second end.
The intake system may further comprise a cooler configured to cool the flow of inlet air within the inlet duct. The chamber may be provided downstream of the cooler. The chamber may be provided upstream of the cooler. The intake system may further comprise one or more additional chambers provided in fluid communication with the inlet duct. The additional chambers may comprise additional movable elements provided within the additional chambers. The additional chambers may comprise additional actuators configured to vary the positions of the additional movable elements. The additional actuators may be configured to vary the positions of the movable elements and thereby vary the volumes of the additional chambers. Any of the features described herein with reference to the chamber may apply equally to the additional chamber.
At least one of the additional chambers is provided upstream of the cooler. Additionally or alternatively, at least one of the additional chambers may be provided downstream of the cooler. The chamber and/or actuator may be configured to adjust a frequency of pressure waves within the inlet air. Additionally or alternatively, the chamber and/or actuator may be configured to generate pressure waves within the inlet air at a desired frequency.
The chamber and/or actuator may be configured such that a frequency of pressure waves within the inlet air substantially corresponds to a desired frequency at which the pressure waves provide enhanced induction for the engine. For example, the chamber and/or actuator may be configured to adjust a frequency of existing pressure waves within the inlet air and/or to generate pressure waves at the desired frequency.
The chamber and/or actuator may be configured such that high pressure waves within the inlet air compress the inlet air within the cylinders e.g. when a corresponding engine inlet is open. The chamber and/or actuator may be configured such that the frequency of pressure waves within the inlet air is substantially equal to the second harmonic frequency of the engine running speed, e.g. twice the engine running speed.
The chamber and/or actuator may be configured such that gases within the chamber resonate at a frequency at which the pressure waves within the intake duct provide enhanced induction for the engine. The chamber and/or actuator may be configured to generate a pressure wave within the inlet duct at a frequency that is substantially equal to a desired frequency at which the pressure waves within the inlet duct provide enhanced induction for the engine.
According to another aspect of the present disclosure, there is provided a method of providing enhanced induction for an engine, the engine comprising an intake system comprising: an intake duct configured to carry inlet air to cylinders of the engine; a chamber provided to one side of the intake duct and in fluid communication with the intake duct; a movable element provided within the chamber; and an actuator configured to vary the position of the movable element and thereby vary a volume of the chamber able to receive inlet air from the intake system. The method for varying a volume of the chamber comprises: varying the position of the movable element at a frequency to adjust pressure variations within the intake system, wherein the frequency varies according to the rotational speed of the engine.
The position of the movable element may be varied such that a natural frequency of pressure variations within the intake duct may be substantially equal to a frequency at which the pressure variations may provide enhanced induction for the engine. Additionally or alternatively, the position of the movable element may be varied such that pressure variations may be generated within the intake duct at a frequency substantially equal to the frequency at which the pressure variations may provide enhanced induction for the engine.
The position of the movable element may varied such that pressure variations may be provided within the intake duct with a natural frequency substantially equal to the second harmonic frequency of the engine running speed.
To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.